<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>首页</title>
</head>
<body>
    <h1>尚硅谷</h1>
    <button>点击获取用户数据</button>
    <script>
        const btn = document.querySelector('button')

        btn.onclick = function(){
            const x = new XMLHttpRequest()
            // 这里满足同源策略，url可以简写
            x.open("GET",'/data')
            // 发送
            x.send()
            // 
            x.onreadystatechange = function(){
                if (x.readyState === 4) {
                    if (x.status >= 200 && x.status <= 300) {
                        console.log(x.response);
                    }
                }
            }
        }
    </script>
</body>
</html>